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Scorch Marks on 2K Plug


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#1 Habib Khan Awan

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Posted 27 July 2018 - 08:36 AM

Hey everyone, ran into a problem with a piece of studio gear yesterday and wanted to ask some of the more knowledgable members before I started going checking everything out.

 

Client ran a 10 hour shoot on the stage yesterday and everything seemed fine. However after the shoot wrapped the DP told me that he had a problem with the Arri 2K fresnel. Seems he had it plugged into our 2K Magic Gadget Pro Dimmer, and when they went to unplug it one of the electricians noticed that the header cable was extremely hot. Then when they unplugged it they saw scorch marks on one of the Edison connector pins. 

 

I took a look at the plug itself and was surprised to see that the plug is a 15amp/125v connector, seeing as I was always taught that 2Ks ran at least ~16/17amps. Is this a normal connector for the unit? The Pro Dimmer states that 2K watts is the peak load, and its female Edison connector is also rated for 15amp/125v, but my math says that this shouldn't work because the fixture is pulling more than 15amps at full power.

 

Granted it was on a dimmer and I have no idea how much they dimmed it down, it could'v been enough to put it just at the 15amp limit, but 15amp shouldn't scorch the pins. Could this be as simple as a dirt/dust in the female plug, or possibly just a loose connection in the wiring of either the dimmer or header cable?


Edited by Habib Khan Awan, 27 July 2018 - 08:38 AM.

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#2 Adrian Sierkowski

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Posted 27 July 2018 - 12:19 PM

You'll have the same problem with M18s, often, as technically, yes, they are 15A connectors on the end of them. Same with stingers, they are also 15A as the "real"  20A plugs have that side-ways "T" on them:

 

hubbell-insulgrip-heavy-duty-5-20p-ediso

 

That's a real 20A connector-- but good luck finding a place to plug it in!


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#3 Habib Khan Awan

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Posted 27 July 2018 - 01:24 PM

Hmm that's strange. If that's the case then why do manufacturers even bother with supplying you with the 15amp connector if they know it wont hold? I feel like this is just a recipe for disaster.

 

Any possible methods to help keep the cable cool? I don't want to have it melt and fuse to the magic gadget.


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#4 Ed Conley

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Posted 27 July 2018 - 03:42 PM

The good quality 15amp connectors are built the same as the 20amp with the side blade.

 

 

 

 

You just smoked the connector because it was on too long.

 

Turn off the lights when not shooting.

 

 

anything past 3 hours continuous use should follow the 80% rule too.


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#5 JD Hartman

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Posted 27 July 2018 - 05:40 PM

Could have been the connector on the Magic Gadget being worn from being used so many times. The blades of a Hubbell are gripped by spring tension.  Not a good grip, more resistance and arcing. Have you never experienced a wall outlet so worn, the cord falls out from its own weight?


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#6 Guy Holt

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Posted 28 July 2018 - 06:17 AM

... why do manufacturers even bother with supplying you with the 15amp connector if they know it wont hold? I feel like this is just a recipe for disaster.  Any possible methods to help keep the cable cool? ....

 

Many manufacturers, like Arri, won't terminate the power cord when they sell you the light for this reason.  For the same reason many TV studios use 20A stage pins instead of the 15A U-ground Edison plugs.  The problem arises when rental houses put the Edison plugs on lights so that they can be plugged into wall sockets.  As Adrian Sierkowski mentions above the problem is even worse with M18s.

 

Even if it is on a dedicated 20A circuit the ballast, cable, and/or the wall receptacle may overheat because the draw of an 1800W HMI is just too close to the threshold of a 20A circuit to operate reliably. The Arri 1800W ballast has an Apparent Power of 2250VA (2600 Max according to the ballast manual) which means it will draw up to 19.5 amps at 115V. Operating this close to the threshold, if there is any line loss from a long cable run, or increased resistance from an overheated/under-rated plug end, the draw of the ballast will climb over 20 Amps.

 

The same is true of operating them on the 20A circuits of portable putt-putt generators.  To the problem of line loss and overheating plug ends, you have the added problem that as you add load on portable generators their voltage output drops.  It is not uncommon for a generator to drop 10-15 volts under full load.  The 1800W ballast that drew 19.5 Amps at 115 Volts will draw 21.4 Amps at 105 Volts.

 

For these reasons, I am convinced that the 1800W power class was designed primarily for the EU market where its Apparent Power of 2250VA fits comfortably in a 13A/230V circuit. Here they work best on a real film distribution system where every circuit is 20 Amps, you know what is on the circuit because you are loading it yourself, and you are bringing the receptacle to the light because you are distributing the power yourself from a tie in or generator.  When you can run a 60A whip and drop a Snack Box next to the light you won’t have a problem. But, if your style of shooting requires that you run multiple stingers to plug into a wall or generator outlet, you will likely have problems with the plug ends or receptacle overheating and causing the breaker to overheat and trip. 

 

I have found that the only reliable way to power a 1800W Baby Max on wall out-lets or on portable gas generators is from a 240V circuit through a 240v-to-120v step-down transformer.  A transformer will convert the 240V output into a single large 120V circuit that is more capable of powering the 19.5A load of a 1800W Baby Max. If you outfit the transformer with a 60A Bates receptacle, it enables you to use a real film style distro system that will allow you to move the generator  off set (where it won’t be heard),  minimize line loss over a long cable run, and provide plug-in pockets close to the ballasts. If you tap the transformer to boost the voltage slightly, it can compensate for the voltage drop on the generator and line loss on the cable, and provide the M18 ballast full line level on set.

 

A transformer will also enable you to run 1800W Arri Baby Maxs on house power from common 240v household outlets as well. Just like it does with a generator, a transformer will step down the 240V power of common high voltage household outlets to a single 120V circuit capable of powering multiple 1800W Baby Maxs. Common 240V sources found on interior locations include Range Plugs, Dryer Plugs, and special receptacles installed for Window Air Conditioners. By giving you access to more house power through common 240V household outlets, a transformer also enables you to run a real distro system without the need for a dangerous tie-in or expensive tow generator.

 

For more detailed information on successfully operating the Arri M18 in 120V land, I would suggest you read a white paper I wrote on the use of portable generators in motion picture production.

 

BoxBookLinkGenSetFP.jpg

 

The white paper is cited in the 4th Edition of Harry Box's “Set Lighting Technician's Handbook" and featured on the companion website. Of the article Harry Box exclaims:

 

“Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working."

 

Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before."

 

The article is available online at http://www.screenlig...generators.html.

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rentals & Sales in Boston


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#7 Phil Rhodes

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Posted 28 July 2018 - 07:24 AM

I suspect my disdain for all things UK is well known, but I have to say that if I were to found a country tomorrow and be asked to specify its mains electrical system, I know how I'd do it. Putting 15A connectors on 20A loads is... a  terrible, terrible workaround?


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#8 Adrian Sierkowski

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Posted 28 July 2018 - 10:50 AM

In the end, this is why we have spare hubbles on the truck. I used to, moons ago, have 20A ones, but I have no idea where to find them anymore. Me things something changed in the electrical code at one time to give us the sideways T.

It doesn't always happen; but it does happen.


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#9 timHealy

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Posted 28 July 2018 - 11:12 PM

Any loose connections in any plug will increase resistance which will increase heat which starts to burn up. A perfectly wired 15 amp plug will last a long time even on a 2k. But one where the connections arent made well or has screws that have come loose will be toast.

While I do like Magic Gadget products, dont use a 2k light with a 2k magic gadget. You are maxing it out every time and itll eventually heat up and short out. Better off with a 2k variac or a 2.4k dimmer

Tim

Edited by timHealy, 28 July 2018 - 11:13 PM.

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